[125.04] X-ray Absorption by the Intergalactic Medium

Most of the baryons at low and moderate redshift could
reside in the intergalactic medium in the form of highly
ionized gas at temperatures of T ~106 - 108 K.
The H-like and He-like ions of the heavy elements (like O,
Si, Fe) could produce absorption features - the so-called
``X-ray Forest'' - in the X-ray spectrum of a background
quasar (Perna & Loeb 1998, Hellsten et al. 1998). In this
work we give a semi-analytic calculation of the X-ray forest
distribution in various cosmologies based on the
Press-Schechter formalism, following Perna & Loeb (1998).
We then perform N-body simulations and find that numerical
and analytic results fit very well. We will have Chandra GTO
observations for two high redshift quasars and compare them
with our predictions.

This work is supported in part by NASA contract NAS 8-38249.

The author(s) of this abstract have provided an email address
for comments about the abstract:
fangt@space.mit.edu